Environmentally responsible derivation

It starts with an ordinary noun source and an ordinary verb sustain and eventually works its way to the adverb sustainably as a modifier of a verb source, strikingly in the split infinitive construction to sustainably source, which Wilson Gray reported in an ADS-L posting on the 11th, citing a General Mills ad in which to sustainably source oats figures prominently.

(You might at first think that (to) sustainably source is a 2-part back-formed verb (2pbfV) derived from the PSP-headed adjectival phrase sustainably sourced, but sustainably source alternates with source sustainably, so it looks like nothing more exotic than adverbial modification — but still with lots of semantic interest.)

On to the General Mills site, which is in love with sustainably source as a BSE form (and also a PRS). From the General Mills blog on 10/10/17 by John Wiebold (relevant phrases boldfaced):

On track to sustainably source oats

Our beloved Cheerios were named Cheeri-Oats when they launched in 1941. So you know that oats have been at the core of our business for a long time. Dating back to 1928, in fact.

Today, nearly four years into our commitment to sustainably source our ingredients, we are well on our way – particularly with oats.

As a global food company, our business depends on quality ingredients being grown and available to us every year. We see the ingredients we buy as a way to be transparent about where and how crops for General Mills foods are grown. So, in 2013, we set out to sustainably source 100 percent of our ten priority ingredients by 2020.

We sustainably source 60 percent of our oats, and expect to hit 75 percent by the end of next May.

We’ve already achieved our target on palm oil and are very close on fiber packaging.

These with the adverb sustainably preceding the verb form it modifies. But there are also examples with the adverb following, as here:

We make every effort to source our ingredients sustainably, cut waste, and use eco-friendly packaging. (St. Ives skin care site)

To get to such examples, we start with the noun source and the verb sustain. From NOAD:

[1] noun source: a place, person, or thing from which something comes or can be obtained

[2] verb sustain: [with object] [a] strengthen or support physically or mentally: this thought had sustained him throughout the years | (as adjective sustaining): a sustaining breakfast of bacon and eggs. [b] cause to continue or be prolonged for an extended period or without interruption: he cannot sustain a normal conversation.

From [1], we get, by verbing, the relatively recent

[1′] verb source: [with object]obtain from a particular source: each type of coffee is sourced from one country.

And in turn from this, the forms

[1′ PRP] sourcing, usable as a N

[1′ PSP] sourced, usable as an Adj (in a predicate or modifying a N)

Then from [2], a derived Adj in –able, with a general sense [a] and also a highly specialized sense [b]: